Semiconductor light-emitting device

ABSTRACT

A semiconductor light emitting device (A) includes an elongated substrate ( 1 ) formed with a through-hole ( 11 ), a first, a second and a third semiconductor light emitting elements ( 3 R,  3 G,  3 B) mounted on the main surface of the substrate ( 1 ), and an electrode ( 2 R) electrically connected to the first semiconductor light emitting element ( 3 R) and extending to the reverse surface of the substrate ( 1 ) via the through-hole ( 11 ). The first semiconductor light emitting element ( 3 R) and the through-hole ( 11 ) are positioned between the second semiconductor light emitting element ( 3 G) and the third semiconductor light emitting element ( 3 B) in the longitudinal direction of the substrate ( 1 ). The second semiconductor light emitting element ( 3 G) is arranged closer to one end of the substrate ( 1 ), whereas the third semiconductor light emitting element ( 3 B) is arranged closer to the other end of the substrate ( 1 ).

TECHNICAL FIELD

The present invention relates to a light emitting device including aplurality of semiconductor light emitting elements, in particular, to aside-view type light emitting device.

BACKGROUND ART

FIG. 4 illustrates an example of a conventional semiconductor lightemitting device (see Patent Document 1 identified below, for example).The semiconductor light emitting device X illustrated in the figureincludes a substrate 91 and three semiconductor light emitting elements93R, 93G, 93B mounted on the main surface of the substrate 91.Specifically, the substrate 91 is provided with electrodes 92R, 92G, 92Bon which the semiconductor light emitting elements 92R, 92G, 92B arebonded, respectively. The substrate 91 is further provided with a commonelectrode 92C, to which the semiconductor light emitting elements 93R,93G, 93B are electrically connected via wires. The semiconductor lightemitting elements 93R, 93G, 93B are surrounded by a case 95 made of aresin. The semiconductor light emitting device X is designed as aside-view type light emitting device to be mounted on e.g. a printedcircuit board with a longitudinal side surface of the substrate 91utilized as the mount surface.

Patent Document 1: JP-A-2006-24794

In recent years, there is a demand for size reduction of semiconductorlight emitting devices. As to the side-view type semiconductor lightemitting device described above, it is demanded to reduce the projectingamount (i.e., height) of the light emitting device from the printedcircuit board on which the light emitting device is mounted. However,the reduction of the projecting amount means the reduction of the areaof the main surface of the substrate 91, i.e., the reduction of thespace required for placing the semiconductor light emitting elements93R, 93G, 93B and the wires connected to the light emitting elements.Generally, as the space becomes narrower, it becomes more technicallydifficult to arrange necessary circuits in the space. Thus, with theconventional structure of the semiconductor light emitting device X,there is a limit on the size reduction.

DISCLOSURE OF THE INVENTION

The present invention has been proposed under the circumstancesdescribed above. It is therefore an object of the present invention toprovide a semiconductor light emitting device suitable for sizereduction.

A semiconductor light emitting device provided according to the presentinvention includes an elongated substrate, a first, a second and a thirdsemiconductor light emitting elements, and an electrode. The substratehas a main surface in the form of an elongated rectangle, a reversesurface opposite to the main surface, a mount surface extending betweenthe main surface and the reverse surface. The substrate has a first endand a second end spaced from each other in the longitudinal direction ofthe substrate. The substrate is formed with a through-hole extendingfrom the main surface to the reverse surface. The first, the second andthe third light emitting elements are mounted on the main surface of thesubstrate. The electrode is electrically connected to the firstsemiconductor light emitting element and extends to the reverse surfaceof the substrate via the through-hole. The first semiconductor lightemitting element and the through-hole are positioned between the secondsemiconductor light emitting element and the third semiconductor lightemitting element in the longitudinal direction of the substrate. Thesecond semiconductor light emitting element is arranged closer to thefirst end of the substrate, whereas the third semiconductor lightemitting element is arranged closer to the second end of the substrate.

Preferably, the semiconductor light emitting device further includes awire, and a pad formed on the main surface of the substrate. The wirehas a first end bonded to the first semiconductor light emitting elementand a second end bonded to the pad. The pad is arranged at a positiondeviated from the second semiconductor light emitting element toward thefirst end of the substrate in the longitudinal direction of thesubstrate.

Preferably, the semiconductor light emitting device of the presentinvention further includes an additional wire for connecting the secondsemiconductor light emitting element and the pad to each other.

Preferably, the main surface of the substrate has a side edge extendingin the longitudinal direction of the substrate, and the firstsemiconductor light emitting element is positioned closer to the sideedge than the second and the third semiconductor light emitting elementsare.

Preferably, the first semiconductor light emitting element is smaller insize than the second and the third semiconductor light emittingelements.

Preferably, the first semiconductor light emitting element is adapted toemit red light. One of the second and the third semiconductor lightemitting elements is adapted to emit blue light, whereas the other oneof the second and the third semiconductor light emitting elements isadapted to emit green light.

Other features and advantages of the present invention will become moreapparent from the detailed description given below with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view illustrating an example of a semiconductor lightemitting device according to the present invention.

FIG. 2 is a rear view illustrating the semiconductor light emittingdevice of FIG. 1.

FIG. 3 is a sectional view taken along lines III-III in FIG. 1.

FIG. 4 is a plan view illustrating an example of a conventionalsemiconductor light emitting device.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred embodiment of the present invention is described below withreference to the accompanying drawings.

FIGS. 1-3 illustrate an example of a semiconductor light emitting deviceaccording to the present invention. The illustrated light emittingdevice A includes an elongated insulating substrate 1, electrodes 2R,2G, 2B, 2C, semiconductor light emitting elements 3R, 3G, 3B, wires 4R,4G, 4B, a case 5 and a transparent protective resin 6 (FIG. 3). Thelight emitting device A is designed as a side-view type light emittingdevice to be mounted with a longitudinal side surface of the substrate 1(lower surface in FIGS. 1-3) utilized as the mount surface. Thesemiconductor light emitting elements 3R, 3G and 3B are adapted to emitred light, green light and blue light, respectively, which are combinedto emit white light. The light emitting device A has a length L of about2.7 mm, a height H of about 0.5 mm and a width W of about 0.95 mm. Foreasier understanding, the illustration of the protective resin 6 isomitted in FIG. 1.

The substrate 1 is made of e.g. a glass fiber-reinforced epoxy resin andin the form of an elongated rectangle. The substrate 1 includes a mainsurface on which the three semiconductor light emitting devices 3R, 3G,3B are mounted, and a reverse surface opposite to the main surface. Thesubstrate 1 is formed with a through-hole 11 and a plurality of grooves12R, 12G, 12B, 12C. As illustrated in FIG. 3, the through-hole 11extends from the main surface to the reverse surface of the substrate 1(i.e., in the thickness direction of the substrate 1). The grooves 12R,12B, 12G, 12C are provided in the mount surface of the substrate 1(i.e., the lower surface in FIGS. 1-3) so as to be separated from eachother and extend in the thickness direction of the substrate 1. Thesubstrate 1 has a length of about 2.7 mm, a height of about 0.5 mm and awidth of about 0.5 mm. The through-hole 11 has an inner diameter ofabout 0.15 mm.

The electrodes 2R, 2G, 2B, 2C are made of a plating layer of Cu, Ni orAu, for example, and formed on the main surface, the side surface (mountsurface) and the reverse surface of the substrate 1. The electrodes 2R,2G, 2B, 2C are utilized for supplying power to the semiconductor lightemitting elements 2R, 2G, 2B and mounting of the light emitting deviceA.

The electrode 2R is connected to the semiconductor light emittingelement 3R and includes a bonding pad 2Ra, a first annular portion 2Rb,a cylindrical portion 2Rc, a second annular portion 2Rd, a strip portion2Re, a reverse surface portion 2Rf and a mount portion 2Rg. The bondingpad 2Ra is provided on the main surface of the substrate 1 at the centerin the longitudinal direction, and the semiconductor light emittingelement 2R is bonded to the bonding pad 2Ra. In the illustrated example,the bonding pad 2Ra is X-shaped. The first annular portion 2Rb adjoinsthe bonding pad 2Ra in the width direction of the substrate 1 (heightdirection) and surrounds the opening of the through-hole 11 on the mainsurface of the substrate 1. The cylindrical portion 2Rc (see FIG. 3) isformed to cover the inner surface of the through-hole 11. The secondannular portion 2Rd surrounds the opening of the through-hole 11 on thereverse surface of the substrate 1. As illustrated in FIG. 2, the stripportion 2Re extends from the annular portion 2Rd toward an end of thesubstrate 1 in the longitudinal direction. The reverse surface portion2Rf is provided on the reverse surface of the substrate 1 to surround acorner. The reverse surface portion is utilized for promoting formationof a solder fillet in mounting the light emitting device A on a circuitboard. The mount portion 2Rg is formed to cover the wall surface of thegroove 12R and utilized for mounting of the light emitting device A.

The electrodes 2B and 2G serve to supply power to the semiconductorlight emitting elements 2B and 2G and include bonding pads 2Ba, 2Ga,semi-annular portions 2Bb, 2Gb, mount portions 2Bc, 2Gc and reversesurface portions 2Bd, 2Gd, respectively. The bonding pads 2Ba and 2Ga,on which the semiconductor light emitting elements 3B and 3G are bonded,respectively, are arranged to be spaced from each other in thelongitudinal direction of the substrate 1 so as to face toward eachother across the through-hole 11. In the illustrated example, thebonding pads 2Ba, 2Ga and the through-hole 11 are aligned in thelongitudinal direction of the substrate 1. The bonding pads 2Ba and 2Gaare X-shaped. The semi-annular portions 2Bb, 2Gb are arranged to reach along side of the substrate 1 and surround the openings of the grooves12B and 12G, respectively, on the main surface of the substrate 1. Thesemi-annular portions 2Bb, 2Gb are provided at locations deviated fromthe bonding pads 2Ba, 2Ga toward the two ends of the substrate 1 in thelongitudinal direction. The mount portions 2Bc and 2Gc are formed tocover the grooves 12B and 12G, respectively, and utilized for mountingof the light emitting device A. The reverse surface portions 2Bd and 2Gdsurround the openings of the grooves 12B and 12G on the reverse surfaceof the substrate 1, respectively, and are utilized for promotingformation of a solder fillet in mounting the light emitting device A.

The electrode 2C is an anode common electrode electrically connected tothe anode electrodes (not shown) of the semiconductor light emittingelements 3R, 3G, 3B. The electrode 2C includes two pads 2Ca for wireconnection (the right pad 2Ca and the left pad 2Ca in FIG. 1), a stripportion 2Cb, an arcuate portion 2Cc, a mount portion 2Cd and a reversesurface portion 2Ce. Wires 4R and 4G are bonded to the right pad 2Ca,whereas a wire 2B is bonded to the left pad 2Ca. The two pads 2Ca arespaced from each other in the longitudinal direction of the substrate 1.In the illustrated example, the two pads 2Ca are provided on the mainsurface of the substrate 1 at locations close to the upper surface (thesurface opposite to the mount surface) of the substrate 1. In thelongitudinal direction of the substrate 1, the left pad 2Ca is providedat a location deviated from the bonding pad 2Ba toward the left end ofthe substrate 1, whereas the right pad 2Ca is provided at a locationdeviated from the bonding pad 2Ga toward the right end of the substrate1. That is, in the longitudinal direction of the substrate 1, the leftpad 2Ca is positioned between the bonding pad 2Ba and the left end ofthe substrate 1, whereas the right pad 2Ca is positioned between thebonding pad 2Ga and the right end of the substrate 1. The strip portion2Cb is formed along a long side and a short side of the main surface ofthe substrate 1. Part of the strip portion 2Cb (the part extendingbetween two pads 2Ca) connects the two pads 2Ca to each other. Thearcuate portion 2Cc is formed to surround the opening of the groove 12Con the main surface of the substrate 1. The mount portion 2Cd is formedto cover the groove 12C of the substrate 1 and utilized for mounting ofthe light emitting device A. The reverse surface portion 2Ce surroundsthe opening of the groove 12C on the reverse surface of the substrate 1and is utilized for promoting formation of a solder fillet in mountingthe light emitting device A.

The semiconductor light emitting elements 3R, 3G and 3B are fixed to thebonding pads 2Ra, 2Ga and 2Ba via e.g. conductive paste, respectively.As will be understood from FIG. 1, the three semiconductor lightemitting elements 3R, 3G, 3B are at positions corresponding to the threevertices of a triangle. Specifically, the center of the semiconductorlight emitting element 3R is at a position corresponding to the vertexof an isosceles triangle, whereas the center of each of thesemiconductor light emitting elements 3B and 3G is at a positioncorresponding to an end of the base of the isosceles triangle. Further,the respective centers of the semiconductor light emitting elements 3Band 3G are positioned on a hypothetical straight line extending in thelongitudinal direction of the substrate 1. The center of thesemiconductor light emitting element 3R is closer to a longitudinal edge(upper edge in FIG. 1) of the main surface of the substrate 1 than thecenters of the semiconductor light emitting elements 3B and 3G are. Therectangular surface of the semiconductor light emitting element 3Rillustrated in FIG. 1 is a square having sides of about 0.15 mm. Therectangular surface of each of the semiconductor light emitting elements3G and 3B similarly illustrated in FIG. 1 is a square having sides ofabout 0.2 to 0.3 mm. In this way, the semiconductor light emittingelement 3R, which is adapted to emit red light, is smaller in size thanthe other two semiconductor light emitting elements 3G and 3B.

The wires 4R, 4G, 4B are made of e.g. gold (Au) and electrically connectthe anode electrodes (not shown) of the semiconductor light emittingelements 3R, 3G, 3B to the electrode 2C. As illustrated in FIG. 1, theleft end of the wire 4R is connected to the semiconductor light emittingelement 3R, whereas the right end of the wire 4R is connected to theright pad 2Ca. The connection point of the right end of the wire 4R ison the right side of the semiconductor light emitting element 3G in thelongitudinal direction of the substrate 1. The left end of the wire 4Gis connected to the semiconductor light emitting element 3R, whereas theright end of the wire 4G is connected to the right pad 2Ca. That is,both of the wires 4R and 4G are connected to the right pad 2Ca at theirright ends. The left end of the wire 4B is connected to the left pad2Ca, whereas the right end of the wire 4B is connected to thesemiconductor light emitting element 3B.

The case 5 is a frame-shaped member made of e.g. a white resin andsurrounds the semiconductor light emitting elements 3R, 3G, 3B, as willbe understood from FIGS. 1-3. The protective resin 6 is made of atransparent resin which transmits light emitted from the semiconductorlight emitting elements 3R, 3G, 3B and fills the space surrounded by thecase 5. The protective resin 6 protects the semiconductor light emittingelements 3R, 3G, 3B.

As illustrated in FIGS. 2 and 3, the reverse surface of the substrate 1is formed with a resist film 7. The resist film 7 prevents unfavorableconnection of the electrodes 2R, 2G, 2B, 2C via solder in the process ofmounting the light emitting device A. The resist film 7 also serves toprotect the strip portion 2Re. The opening of the through-hole 11 isclosed by the resist film 7 on the reverse surface. With thisarrangement, liquid resin as the material of the protective resin 6 isprevented from leaking through the through-hole 11. As illustrated inFIG. 2, the resist film 7 has an asymmetric shape so that the mountingof the light emitting device A with wrong polarity is prevented.

The advantages of the light emitting device A are described below. Inthe above-described arrangement, of the electrode 2R, only the bondingpad 2Ra and the first annular portion 2Rb are provided on the mainsurface of the substrate 1, and the other portions are provided on theinner wall of the through-hole 11 or the reverse surface or mountsurface of the substrate 1. In this arrangement, the electrode 2R doesnot include a portion extending from the semiconductor light emittingelement 3R to the periphery of the substrate 1. This is suitable formounting the three semiconductor light emitting elements 3R, 3G, 3B inthe narrow region of the main surface of the substrate 1. Further, byarranging the three semiconductor light emitting elements 3R, 3G, 3B ina triangular shape, it is possible to position the semiconductor lightemitting elements 3G and 3B close to the semiconductor light emittingelement 3R and also position the semiconductor light emitting elements3G and 3B close to each other. Thus, the light emitted from thesemiconductor light emitting elements 3R, 3G, 3B is properly combinedtogether, whereby ideal white light is obtained.

As noted above, an end of the wire 4R bonded to the semiconductor lightemitting element 3R is bonded to the right pad 2Ca at a position on theright side of the semiconductor light emitting element 3G in thelongitudinal direction of the substrate 1. With this arrangement, it isnot necessary to provide a space for bonding the wire 4R within thetriangular region surrounded by the three semiconductor light emittingelements 3R, 3G, 3B, which holds true for the other two wires 4G and 4B.This is suitable for arranging the semiconductor light emitting elements3R, 3G, 3B close to each other. Moreover, bonding the two wires 4R and4G to the single pad 2Ca occupies less space than preparing anindividual pad for each of the wires 4R and 4G.

The semiconductor light emitting element 3R, which is positioned at thecenter in the longitudinal direction of the substrate 1, is made smallerin size than the other two semiconductor light emitting element 3G and3B, as noted above. This is suitable for arranging the semiconductorlight emitting elements 3R, 3G, 3B close to each other. Further, clearwhite light is obtained by sandwiching the semiconductor light emittingelement 3R for emitting red light between the semiconductor lightemitting elements 3R and 3B for emitting green light and blue light.

The semiconductor light emitting element to be used in the presentinvention is not limited to the type designed to be bonded at the lowersurface, with a wire bonded to the upper surface. For instance, use maybe made of a semiconductor light emitting element of the type in whichtwo wires are to be bonded to the upper surface. Alternatively, use maybe made of a semiconductor light emitting element of the flip chipmounting type which does not use a wire.

1-6. (canceled)
 7. An LED package comprising: a support member having arecess; a first LED chip disposed at a bottom of the recess; a secondLED chip disposed at the bottom of the recess and overlapping with thefirst LED chip as viewed in a first direction parallel to the bottom ofthe recess; and a third LED chip disposed between the first LED chip andthe second LED chip and having a portion overlapping with both the firstLED chip and the second LED chip as viewed in the first direction,wherein the third LIED chip has a center located outside of a regionthrough which the first LED chip and the second LED chip face each otherin plan view.
 8. The LED package according to claim 7, wherein the firstLED chip and the second LED chip are same in size and shape in planview.
 9. The LED package according to claim 7, further comprising afirst wire, a second wire and a third wire that are connected to thefirst LED chip, the second LED chip and the third LED chip,respectively.
 10. The LED package according to claim 9, furthercomprising a common conductor elongated in the first direction, whereinthe first wire, the second wire and the third wire are bonded at an endthereof to the common conductor.
 11. The LED package according to claim10, wherein the support member comprises a side wall portion forming therecess, and at least a part of the common conductor is covered with theside wall portion.
 12. The LED package according to claim 10, furthercomprising an additional conductor opposite to the common conductor withrespect to the third LED chip, wherein the third LED chip iselectrically connected to the additional conductor.
 13. The LED packageaccording to claim 11, wherein the side wall portion forms a closed loopthat surrounds the first LED chip, the second LED chip and the third LEDchip in plan view.
 14. The LED package according to claim 11, whereinthe side wall portion is made of a white resin.
 15. The LED packageaccording to claim 11, wherein the support member includes a baseportion formed integral with the side wall portion, the base portion hasan obverse surface and a reverse surface opposite to the obversesurface, the obverse surface supports the first LED chip, the second LEDchip and the third LED chip, and the base portion is formed with athrough-hole extending from the obverse surface to the reverse surface.16. The LED package according to claim 7, further comprising aprotection resin member filled in the recess and covering the first LEDchip, the second LED chip and the third LED chip.